Many uses are known for carbon and graphite foam materials, and a number of processes have been developed for making carbon and graphite foams. Known uses include uses such as a heat sink, a heating element, an electrical conductor, a lightweight form filling body for composite structures, cryostatic devices for cooling detectors such as infrared, electron, X-ray or other radiation detectors, a fuel cell element, a membrane for separation of conductive fluids, and combinations of these. Graphite has a very high conductivity, and foams made of graphite share this characteristic.
Most processes for making graphite foams include some combination of the application of heat and inert gases under high pressure to a material such as pitch which can be converted to graphite, followed by changes in pressure and/or temperature in which bubbles or voids are caused to form in the material, and subsequent carbonization and graphitization. Such processes generally produce foams having pore sizes substantially greater than ten microns and are not capable of producing microporous graphite foams having a pore size less than about ten microns, while still having features such as a low bulk density, low brittleness and acceptable physical strength. The low brittleness and physical or mechanical strength are needed for subsequent handling and machining into items having a shape other than a relatively simple molded shape. Low bulk density is needed for light weight. While prior art methods could attain some of these characteristics, it has not been possible to attain desired combinations of them together with a microporous structure.
Thus, a need remains for a microporous graphite foam having pore sizes less than ten microns, low bulk density and good physical strength for subsequent handling and machining into items having a shape other than a relatively simple molded shape, while also having the desirable characteristics of graphite, including light weight, high thermal conductivity, electrical conductivity and solderability.